This invention relates to a rotary indicating plate type digital display device.
In rotary indicating plate type digital display devices of a clock, etc., the driving system for a minute drum and an hour drum has heretofore included two types. One of them continuously drives both the minute drum and the hour drum, while the other intermittently drives both the minute drum and the hour drum. With the former type, a shear arises in the indicated characters of the hour and the minute, and hence, the number of hour indicating plates need be made large. Besides, the independent corrections of the hour and the minute are difficult. Further, in order that the change of the minute indication from "59" to "00" and the change of the hour indication may be carried out at the same time, specific minute indicating plates, for example, minute indicating plates for indicating "45" - "59" are provided with projecting pieces, and an engaging spring which shifts to the front of the hour indicating plate in interlocking relationship with the projecting piece is provided between the hour drum and the minute drum. In consequence, the spacing between the hour drum and the minute drum becomes large. Moreover, when a calender mechanism is provided, the date or the day of the week does not change exactly at 12.00 p.m., but errors of several minutes are involved. On the other hand, the latter type requires a driving torque which is greater than in the former. In addition, a comparatively large noise is generated every minute by the intermittent drive and such noise is offensive to the ear.